The eye works like a camera. The colored portion of the eye, or the iris, acts as a shutter to collect the amount of light coming into the eye. The cornea (the clear window of the eye) and the lens, located behind the pupil(the small black dot in the middle of the iris), focuses light rays from the object viewed on the retina to the back of the eye. The optic nerve transmits a signal to the brain. When the signal goes to your brain, it appears right-side up.

What Is Nearsightedness (Myopia)?

The eye is too long and cannot see things that are far away.

What Is Farsightedness (Hyperemia)?
 The eye is too short and cannot see things up close.

 What is Astigmatism?

       Astigmatism is a vision condition in when light entering the eye can't
      be brought to a single focus, resulting in blurred vision at all
distances.

What causes nearsightedness,
    farsightedness, and astigmatism?
 

Presbyopia, Amblyopia, Glaucoma,
and Cataracts

 Q:  What is presbyopia?
       A:  Presbyopia is a vision condition that occurs when the crystalline lens of
             the eye cannot bring far away things into clear images. Presbyopia is a sign of nearsightedness.

Q:  What is amblyopia?
       A:  Amblyopia (lazy eye) is loss of vision in
       one eye that cannot be fully corrected with lenses.
Amblyopia can cause conditions such
       as crossed-eyes (strabismus) or a large difference
       between the two eyes.

Q:  What is glaucoma?
       A:  Glaucoma is a disease in which the fluid pressure in your eyeball
       increases and damages the optic nerve and can cause
blind ness.

Q:  What are cataracts?
       A: A cataract is when the normally clear lens in your eye becomes cloudy. Vision will then become blurred and/or distorted.

Mild Myopia  <-3.00 diopters
Moderate Myopia -3.00 to -6.00 diopters
Severe Myopia -6.00 to -9.00 diopters
Extreme Myopia  >-9.00 diopters